Developers of holographic display are working on a technology that will let speakers and performers deliver speeches and entertain an audience without being there. They'll do it via hologram video projection, in which a filmed performance is presented in a live, 3-D image — like Princess Leia's message to Obi-Wan Kenobi in Star Wars.

In January, the music group Black Eyed Peas performed holographically at an awards show in France. Two small airports in Britain — Manchester and London Luton— have holographic images of staffers explaining security clearance rules. Others to appear via hologram technology in recent years: Former vice president Al Gore, Microsoft founder Bill Gates and British airline and media mogul Richard Branson.